Reference:
▪ Mills, S.J., Christy, A.G., Kampf, A.R., Birch, W.D., Kasatkin, A. (2017): Hydroxykenoelsmoreite, the first new mineral from the Republic of Burundi. European Journal of Mineralogy, 29, 491-497.
Abstract:
We report the new mineral hydroxykenoelsmoreite, which has been approved by the IMA as IMA2016-056. The mineral occurs at the Masaka gold mine, Burundi, as rosettes up to 150μm across of platy crystals up to 20μm wide but < 2μm thick, associated with goethite and galena. Crystals are canary yellow, transparent with a vitreous lustre, and have a pale yellow streak. Hydroxykenoelsmoreite is uniaxial (-)and non-pleochroic. The refractive indices were too high to measure, but the Gladstone-Dale compatibility index predicts nave = 2.065. Crystals are brittle with an irregular fracture, but have perfect cleavage on {0 0 1}. The Mohs hardness is ∼ 3 by analogy with hydrokenoelsmoreite. The mineral is a member of the elsmoreite group of the pyrochlore supergroup, but deviates from the ideal cubic symmetry due mainly to ordering of Fe3+ onto one of twoWsites. Its structure is trigonal, space group R-3, with unit-cell parameters a = 7.313(2), c = 17.863(7) Å, V = 827(1)Å3 and Z = 6. The empirical formula (based on 7 (O + OH) per formula unit (pfu)) is: (□1.668Pb0.315Ca0.009Na0.005K0.003Ba0.001)Σ2(W6+>1.487Fe3+0.357Al0.156)Σ2(O4.119(OH)1.881)Σ6(OH); Raman spectroscopy and bond–valence sums showed that molecular H2O was absent or nearly so. The calculated density is 5.806 g cm-3.
▪ Mills, S.J., Christy, A.G., Kampf, A.R., Birch, W.D., Kasatkin, A. (2017): Hydroxykenoelsmoreite, the first new mineral from the Republic of Burundi. European Journal of Mineralogy, 29, 491-497.
Abstract:
We report the new mineral hydroxykenoelsmoreite, which has been approved by the IMA as IMA2016-056. The mineral occurs at the Masaka gold mine, Burundi, as rosettes up to 150μm across of platy crystals up to 20μm wide but < 2μm thick, associated with goethite and galena. Crystals are canary yellow, transparent with a vitreous lustre, and have a pale yellow streak. Hydroxykenoelsmoreite is uniaxial (-)and non-pleochroic. The refractive indices were too high to measure, but the Gladstone-Dale compatibility index predicts nave = 2.065. Crystals are brittle with an irregular fracture, but have perfect cleavage on {0 0 1}. The Mohs hardness is ∼ 3 by analogy with hydrokenoelsmoreite. The mineral is a member of the elsmoreite group of the pyrochlore supergroup, but deviates from the ideal cubic symmetry due mainly to ordering of Fe3+ onto one of twoWsites. Its structure is trigonal, space group R-3, with unit-cell parameters a = 7.313(2), c = 17.863(7) Å, V = 827(1)Å3 and Z = 6. The empirical formula (based on 7 (O + OH) per formula unit (pfu)) is: (□1.668Pb0.315Ca0.009Na0.005K0.003Ba0.001)Σ2(W6+>1.487Fe3+0.357Al0.156)Σ2(O4.119(OH)1.881)Σ6(OH); Raman spectroscopy and bond–valence sums showed that molecular H2O was absent or nearly so. The calculated density is 5.806 g cm-3.